1. Technical Field
The disclosure generally relates to a thin film transistor.
2. Description of Related Art
Nowadays, thin film transistors have been widely used in display devices to make the display devices become thinner and smaller. A typical thin film transistor includes a channel region, and a source region and a drain region formed at two opposite ends of the channel region, respectively. A gate electrode is formed on the channel region. A source electrode and a drain electrode are formed on the source region and the drain region, respectively. The thin film transistor is turned on or turned off by controlling a voltage applied to the gate electrode.
Generally, the source region and the drain region each are made of an oxide semiconductor material such as InGaZnO, which has a carrier concentration ranging from 1×1015 to 1×1018 cm−3. When the source electrode is applied to the source region, a contact resistance between the source electrode and the source region will have a high value due to the relatively low carrier concentration of the source region. Similarly, a contact resistance between the drain electrode and the drain region will have a high value due to a relatively low carrier concentration of the drain region. The high contact resistances will increase a driving voltage of the thin film transistor and reduce a response speed of the thin film transistor to a control signal.
What is needed, therefore, is a thin film transistor to overcome the above described disadvantages.